In general, a smart key system for vehicles refers to a system in which a driver (or user) carries a FOB key, and a smart key unit of the vehicle (hereinafter, “SMK unit”) analyzes an encrypted code from the FOB key to operate various functional operation units of the vehicle only when the user is authenticated as a normal user, thus preventing the vehicle from being stolen.
That is, if the user carrying the FOB key approaches the vehicle within a predetermined distance, the SMK unit wakes up the FOB key and communicates encryption code data of a transponder embedded in the FOB key to authenticate a normal user ID, and if the user is determined as a normal user, the SMK unit switches on so that various functional operation units installed in the vehicle, such as starting engine, opening/closing the trunk door or side doors, may be in normal operation.
Meanwhile, a signal transfer system when a side door is opened, may be divided into the following two situations: In the first situation, after normal user ID authentication is done, among operation switches of various functional operation units provided in the FOB key, a switch associated with the operation of the side door is directly entered by the user so that a predetermined signal is transmitted to the SMK unit. In the second situation, the normal user ID is authenticated, and then, a triggering signal generated from the handle of the side door is transmitted to the SMK unit.
The triggering signal generated from the handle of the side door may be generated as the user himself pulls the handle of the side door or as the user presses a triggering button provided on the handle of the side door.
A normal user ID authentication process performed between the spraying unit and the FOB key in the conventional smart key system is briefly described below.
First, if the FOB key approaches the vehicle within a predetermined distance or the user himself pulls the handle of the side door, a challenge signal is generated, and the generated challenge signal is modulated or demodulated by the SMK unit, and is then received by an LF receiver of the FOB key. Upon receiving the challenge signal, the FOB key transmits a response signal including an ID code and encryption code by way of an RF transmitter of the FOB key. The RF receiver of the SMK unit receives the response signal, determines whether the received ID code and encryption code match previously stored ID code and encryption code, and only when they match, enables the operation of the functional operation units.
In the conventional smart key system, however, even when the user carrying the FOB key is located away from the vehicle at a predetermined distance or more (for example, the maximum visibility range within which the driver may observe the vehicle), in case a challenge signal is normally transferred from the vehicle to the FOB key (this is referred to as “relay-attack”), the various functional operation units may remain operated by someone else, thus causing the vehicle and equipment in the vehicle to be stolen.
Further, the conventional smart key system cannot recognize a FOB key with copied encryption code data, thus oftentimes putting the vehicle or equipment in high chance of being stolen by a person who carries a copied FOB key with an impure intention.